This invention relates to a monitor for the automated non-invasive measurement of a patient's blood pressure comprising means for automatically inflating and deflating a cuff which is to be applied around a patient's extremity, in particular an arm, a pressure sensor coupled to the airway of said cuff and providing an electronic signal indicative of the cuff pressure, electronic means for calculating the blood pressure from the signals obtained by said pressure sensor, in particular from the oscillations of the pressure signal, pneumatic connecting means attached to said monitor--preferably, the casing thereof--said pneumatic connecting means being provided for connection with a cuff connector and comprising a connector body.
Monitors for the automated non-invasive measurement of blood pressure generally comprise a cuff which is to be applied around a patient's arm or leg. This cuff is inflated in periodic intervals by a pressure pump integrated in the monitor. Subsequent to each inflating of the cuff, it is deflated slowly by means of at least one valve integrated in the monitor.
The deflating process is used to determine the blood pressure of the patient, e.g. the systolic, diastolic or mean blood pressure. This can be achieved, for example, by using a microphone which records the Korotkoff sounds which appear when the arteries open (this method is similar to the manual "auscultation" technique). Another method which is better suited for automated blood pressure recordings is the so-called "oscillometric method". According to this method, the oscillations superimposing the generally decreasing cuff pressure are monitored during the deflating process to determine the various blood pressures (systolic, diastolic or mean). The algorithms used to determine the blood pressure from these oscillations are rather complex; algorithms of this kind have been described in a lot of patent applications. An example out of many other ones is European patent application EP-A-208 520.
Monitors of the kind described above comprise a pneumatic connector, usually of the female type, which is attached to the casing of the monitor. In operation, a second (male) pneumatic connector is inserted in the female connector. The second (male) connector is connected with the cuff by means of a flexible tube. Such a monitor further comprises a pressure sensor coupled to the airway of said cuff and providing an electronic signal indicative of the cuff pressure. Such a pressure sensor is necessary for controlling and monitoring the pressure in the cuff, in particular for monitoring the maximum cuff pressure (i.e. the pressure at maximum inflation--this pressure is not identical to the pressure upon which a safety valve may open!) and for controlling the process of cuff deflation (this is particularly important if the cuff is deflated in single decrementing steps). When using the osillometric method which apparently becomes the most common one in the automated monitoring field, the pressure sensor is further required to record the high-frequency oscillations during the deflating process. Such a pressure sensor or pressure transducer is, for example, shown in EP-A-208 520, cf. reference number 105.
Monitors according to the state of the art comprise a lot of airway tubes, T-connectors and tube nozzles arranged inside the monitor. These connection elements are necessary to connect the pump, one or two valves and one or two pressure sensors to the main airway leading to the pneumatic connector at the front end of the monitor. In these monitors, the pressure sensor is arranged inside the monitor casing, and most commonly it is soldered on a printed circuit board. A tube connects the pressure sensor with the pneumatic connector. Such an arrangement has a lot of disadvantages with respect to manufacturing; in particular, the various tubing elements are expensive and time-consuming to assemble. Furthermore, the tubing elements and the pressure sensors mounted directly on the printed circuit board require a lot of space, particularly board space. Other disadvantages do have physical reasons; in particular, the pressure sensor is positioned relatively distant to the patient, and therefore the pressure recorded by the sensor may not correspond to the actual pressure in the cuff as each tube acts as a pressure resistance. Further, the connection tube may expand, and the volume of the airway system is rather large.
It is therefore a major objective of the present invention to provide a monitor for the automated non-invasive measurement of blood pressure which ensures that the actual cuff pressure is recorded very precisely and which is easy and cost-saving to assemble.